Found in 1948 MIT documentation, this 4-tube amplifier is characterized by its low noise level.
This circuit is from an 80's documentation. The BC108 can be replaced by the BC548 and the 2N3055...
May 2017 - These new Digital to Analog converters from Texas Instruments, available from Mouser...
This circuit prevents the passage of frequencies in a range starting at 1 kHz and can be adjusted...